With development of lightweight automobiles, increasingly stringent energy-saving and environmental protection requirements, many parts of automobiles that were originally made of cast iron and cast steel are changing to light alloys such as aluminum and magnesium alloys. Due to differences in material mechanical properties and forming processes, product structure needs to change during this transformation process, that is, it needs to be changed to a structure suitable for forming alloys such as aluminum and magnesium. As an important forming method for aluminum and magnesium alloys, die casting has advantages of high productivity and high dimensional precision. It has huge advantages and competitiveness in development and production of automotive parts, so it has also become preferred forming process for lightweight automotive parts.
This project takes lightweighting of a cooling water connector casting as an example. Based on calculation results of temperature field, heat node distribution and other calculation results of MAGMASOFT software, cooling water connector casting structure is optimized by reducing wall thickness, setting reinforcing ribs and other measures, so that cast iron parts originally cast by sand casting are changed to aluminum alloy parts suitable for die casting. By calculating die casting forming process of connector such as pouring, cooling, and overflow, a reasonable process plan is determined.
Figure 1 is a model diagram of cooling water connector, which was originally a cast iron part. In order to reduce weight, it is planned to change this product to aluminum alloy and produce it by die casting. Outer contour dimensions of part are 140mm*127mm*48mm, and aluminum alloy material is A380. Its composition is shown in Table 1. Air tightness of product requires a leakage of ≤4.8cm³/min at 150kPa. Appearance of casting cannot have defects such as cold shut and cracks, and internal quality meets ASTM E505A2 level or above.

 

Table 1 Chemical composition of A380 aluminum alloy (%)

 

Figure 1 Schematic diagram of casting structure

 

Figure 2 Comparison diagram of hot spot analysis

 

Figure 3 Temperature distribution of casting after solidification for 9.2s

 

Figure 4 Schematic diagram of process scheme

 

Figure 5 Simulation of aluminum alloy filling process after optimized structure

 

Figure 6 Air pressure distribution diagram

Table 2 Die casting trial process parameter table

 

Figure 7 Actual picture of casting

 

Figure 8 X-ray photo of die casting
With help of hot spot distribution calculation module of MAGMASOFT software, product structure is optimized, so that casting processability of product is improved. Based on optimized product structure, pouring system, cooling system and overflow system of die casting mold are designed, filling and solidification process of aluminum liquid are simulated and analyzed to verify rationality of process scheme. Internal quality inspection of product after die-casting shows that internal quality of casting meets ASTM E505A2 standard and airtightness meets requirements.